1. Field of the Invention
This invention relates to ceramic dielectric compositions for temperature compensating capacitors which have a high dielectric constant and a relatively small temperature coefficient of the dielectric constant with a very excellent linearity.
2. Description of the Prior Art
Up to this time, among ceramic dielectric compositions for temperature compensating capacitors, for example,
(1) CaTiO.sub.3 -La.sub.2 O.sub.3 -TiO.sub.2 system, PA1 (2) SrTiO.sub.3 -CaTiO.sub.3 -(Bi.sub.2 O.sub.3.2TiO.sub.2) system, and PA1 (3) PbTiO.sub.3 -CaTiO.sub.3 -La.sub.2 O.sub.3 -TiO.sub.2 system
are known as compositions with relatively high dielectric constant. However, for example, the composition system (1) has an excellent characteristics in the dielectric loss at high frequencies and in the linearity of the temperature coefficient of a dielectric constant, but has a low dielectric constant to the extent of about 150. By the composition system (2), a composition with high dielectric constant to the extent of about 450 can be obtained, but the temperature coefficient thereof has a poor linearity, and, to the contrary, a composition having the excellent linearity of temperature coefficient of a dielectric constant has a low dielectric constant to the extent of about 250. Further, it is known that a very high dielectric constant, such as 600, can be obtained by the composition system (3). However, in this case, the temperature coefficient of a dielectric constant is undesirably increased and the linearity thereof is very poor. For example, the temperature coefficient varies from N 5000-N 6000 ppm/.degree.C., wherein N indicates that the slope of the temperature coefficient is negative. Thus, by the composition system (3), it is very difficult to obtain a composition with a high dielectric constant, with a relatively small temperature coefficient thereof to the extent of not more than N 2000 ppm/.degree.C. and with an excellent linearity thereof.